This research is part of the AmasSeds Project (A Multi- disciplinary Amazon Shelf Sediment Study), which seeks to understand the physical, chemical and geological processes that affect, or are affected by, particle fluxes on the Amazon shelf. High particulate fluxes occur on the Amazon shelf as a result of the enormous sediment discharge from the Amazon River and the extensive resuspension of fine-grained shelf sediment by tidal processes. This component examines several chemical processes occurring at the Amazon River/ocean boundary which are affected by particle fluxes. The specific topics of research describe: (1) the release of uranium and radium from the particulate phase to the dissolved phase during river/ocean mixing: (2) scavenging of particle-reactive elements from continental shelf waters; and (3) evaluating the effects of suspended sediment concentration on the biological uptake and regeneration of carbon and silicon. This research is part of the AmasSeds Project (A Multi- disciplinary Amazon Shelf Sediment Study), which seeks to understand the physical, chemical and geological proceses that affect, or are affected by, particle fluxes on the Amazon shelf. High fluxes occur on the Amazon shelf as a result of the enormous sediment discharge from the Amazon River and the mixing of fine- grained sediment with river water by the tides. This component of the overall project examines several chemical processes occurring at the Amazon River/ocean boundary which are affected by particle fluxes. An understanding of these processes will help investigators to interpret observations from other river/ocean systems throughout the world.